Mars Facts

Do you know much about Mars? Well if not, read on for some facts about this fascinating planet.

Mars is the only planet whose surface can be seen in detail from the Earth. It is reddish in color, known as the Red Planet, and was named after the bloody red god of war of the ancient Romans.

Mars is the fourth closest planet to the sun. The diameter of Mars is 4,200 miles (6,760 kilometers), a little over half that of the Earth. Mercury is the only planet smaller than Mars.


A lot of astronomers believe that the Solar System is made up of two parts, the Inner Solar System and the Outer Solar System. The Inner Solar System includes Mars, Mercury, Venus and Earth.

These are the planets that are closest to the sun and are called terrestrial planets because they have very solid rocky surfaces.

Mars – Key Stats

 Mass: 1,414,690,904,082,006 billion pounds (641,693,000,000,000 billion kilograms)

Orbit Size (semi-major axis): 141,637,725 miles (227,943,824 kilometers)

Mean Radius: 2,106 miles (3,390 kilometers)

Volume: 101,355,340,933 cubic miles (163,115,609,799 cubic kilometres)

Density: 0.141 ounces per inches³ (3.93 grams per cm³). 0.713 times the density of Earth

Diameter: The diameter of Mars is 4,216 miles (6,785 kilometers)

Orbital Speed: The orbital speed of Mars is 54,133 miles per hour or 24.2 kilometers per second.

Quick Facts

A Mars year is equal to 686.98 days on Earth, which means it orbits the sun every 687 days.

A day on Mars is equal to 24.6 Earth hours.

It is 35 million miles (56,327,040 kilometers) from Earth.

A lot of planets are bigger than Earth. For example, 318 Earths could fit inside of Jupiter. Mars is not quite so big. In fact, Mars is one of only two planets in the solar system to be a lot smaller than Earth. If you looked at the two planets side by side, Earth would be a basketball while Mars is a softball (see below).


Mars is 155 million miles (249 million kilometres) from the sun.

Mars is red because it is rusty. There is a lot of iron in the soil, and the air on Mars has made it turn red-just like rusty iron on Earth.

At its brightest, Mars outshines every other planet apart from Venus.

In 1996 NASA, whilst studying the ALH 84001 meteorite of Martian origin found in Antarctica in 1984, announced that fossilized micro-organisms from Mars might be present in it.

The Surface of Mars

Temperatures on Mars vary from 32°F (0°C) to -148°F (-100°C).

In winter, nighttime temperatures on Mars can drop as low as -191°F (-88°C).

If you weigh 100 pounds (45 kilograms), you would weigh 38 pounds (17 kilograms) on Mars.

The surface of Mars is covered in canyons and valleys. Scientists think that because of this the planet once had water on it.

Just like Earth, Mars’ two poles are covered in ice. The ice becomes thicker in the winter.

Of all the volcanoes in the Solar System, Mars has the tallest. It is called Olympus Mons and it is 15 miles (24 kilometers) high, three times as high as Mount Everest.

Valles Marineris is the largest canyon in the solar system, stretching 2,485 miles (4,000 kilometers) across the surface. If you look at a picture of Mars taken from a telescope, you will see the giant gash that is Valles Marineris.

The Borealis Basin makes up 40% of the planet’s surface, taking up almost the entire northern hemisphere.


Does Mars have Moons or Rings?

Mars doesn’t have any rings.

It does however have two small moons called Phobos and Deimos.

One of Mars’ two moons, Phobos, is slowly getting closer and closer to Mars. Astronomers think that it will eventually crash into the planet.

The History of Mars 

Mars was named after the God of War in Roman mythology.

Asaph Hall discovered Mars in August 1877.

Mars Atmosphere

The atmosphere on Mars is very thin. It is mainly made up of carbon dioxide (95%), nitrogen (2.7%) and argon (1.68%) with some traces of oxygen and water.

Mars had a much thicker atmosphere in the past. Scientists think that this is because the sun’s energy pushed the lighter molecules out of Mars’ atmosphere over millions of years, making it thinner and thinner over time.

Space Missions to Mars

There have been quite a few space missions to Mars, but here are some of the most important ones.

  • Mariner 4: this was the first successful flyby mission to Mars. It launched on November 28, 1964 and arrived at Mars on July 14, 1965.
  • Mariner 9: this was the first successful orbit of Mars. It was launched on May 30, 1971 and began to orbit on November 13, 1971.
  • Viking 1: this was the first successful orbit and landing on the surface of Mars. It was launched on August 20, 1975 and arrived at Mars on July 20, 1976.

More Astronomy facts.